Tat-Gap 19, a peptide inhibitor of connexin43 (Cx43) hemichannels, is derived from the HIV-1 Tat protein transduction domain fused with a nine-amino acid sequence from Cx43 residues 128-136. This compound, at a concentration of 10 µM, effectively suppresses glutamate-induced ATP release in primary rat hepatocytes, indicating inhibition of Cx43 hemichannel activity. Furthermore, Tat-Gap 19 demonstrates therapeutic potential by significantly reducing infarct volume in a mouse cerebral ischemia-reperfusion injury model following middle cerebral artery occlusion (MCAO) at a dosage of 25 mg/kg. Moreover, its intraperitoneal administration at 1 mg/kg per day ameliorates fibrosis and decreases the area of hepatic stellate cells, the precursors to myofibroblasts, expressing α-smooth muscle actin (α-SMA), in a model of thioacetamide-induced liver damage. Additionally, it enhances superoxide dismutase (SOD) activity in hepatic cells from the treated mice, indicating its antioxidative benefits.